During the past some 20 years, a remarkable progress has been made in many areas of genetics, yet the development in genetics of life -genetics of the quality of life - has been rather slow. We choose Fisher's Malthusian parameter of population increase, m, as a measure of quality of biological life. The value of m is dependent upon the life table of an individual. There seems to be an "optimum" combinations of the components in the life table, which maximizes the value of m under a given environmental condition. We propose that the life tables of individuals are under genetic control, and natural selection selects for a group of genotypes having the best life table (optimum combination of the components) which maximizes the m value. Using Drosophila melanogaster as an experimental material, it is aimed 1) to establish a formal genetic basis of factors affecting the components in the life table, and 2) to obtain experimental evidences supporting the hypothesis described above. A special emphasis will be placed on the cytoplasmic factors and their possible interactions with the chromosomal genes.